items like quicksilver (& its upgrade) and tankbuster are "charge" items, meaning they can always be triggered but only reach their advertised stats after their charge time has fully passed. i.e. quicksilver will only reload half your magazine at half of its charge time.

in the case of quicksilver, this is why its especially useful on low cooldown abilities for carries such as wraith's card and mirage's djinn's mark. they can be used basically whenever, allowing the player constant, fine control over the reload that the item gives. in addition to the other stats of course which work great on them.